I’ve thought about a lead Dragonite. While it does lead very well against the 2 most common pokemon of all ultra league time - Swampert and Giratina-A - it gets walled by fairies, steels and Articuno and Lapras are pretty common too. It’s high risk high reward
Does your Swampert have Hydro Cannon? Otherwise it’s a pretty average pick
Blaziken rarely gets clean wins. It’s fun to use, but it usually doesn’t add a lot to the fight other than taking one down
If you are able to put 2 moves on Giratina-A, it complements Swampert very well - and Ancient power can get you wins even in matches you are supposed to lose.
Togekiss is solid, but is walled entirely by quite common Registeels, Melmetals and fire types.
Snorlax - if you run lick + body slam/superpower or eq - is a great pokemon for taking on neutral matchups and giratina/a-mewtwo
A great meta team - it wins consistently but people might be prepared for it - is swampert - giratina-A - snorlax. Your challenges would be:
Lead swampert against a lead water pokemon - you might have to bait shields with hydro cannon and destroy with eq
Shiftry after snorlax is down
A-Muk after swampert is down
Venusaur after Giratina is down
Ignore the getting destroyed by Leafeon Glaceon Umbreon comment, you are more likely to encounter a shiny Gible spawn on your house than encounter this in UL